Sewing machine



June 2, 1936. H R G 5 2,043,149

SEWING MACHINE Filed Sept. 19, 1933 '7 Sheets-Sheet 1 3nventor June 2, 1936. H. F. BRIGGS INVENTOR MW 6 67/69 ATTORN June 1935- H. F. BRIGGS SEWING MACHINE Filed Sept. 19, 1953 7 Sheets-Sheet 3 R Q N 3nnentor Will/M [KI/1%! Gttomeg June 2, 1936. H. F. BRIGGS SEWING MACHINE Filed Sept. 19, 1953 7 Sheets-Sheet 4 INVENTOR ,w/m M66) June 2, 1936. BRlGGs 2,043,149

SEWING MACHINE Filed Sept. 19, 1953 7 Sheets-Sheet 5 A TTORNEY BY z . June 2, 1936. I H. F. BRIGGS SEWING MACHINE Fi led Sept. 19, 1953 7 Sheets-Sheet e w 0 H T M MM? 0 VM H mM WA June 2, 1936. H. F. BRIGGS SEWING MACHINE Filed Sept. 19, 1935 7 Sheets-Sheet '7 llllll lllll-Lvllzlll Patented June 2, 1936 UNITED STATES PATENT. OFFICE.

' Applic ation September is, 193:. Serial no. 1:90.052.

10 Claims.

- My invention relates to sewing machines and more particularly to sewing machines adapted for sewing heavy materials.

In sewing the mouths of paper bags intended to contain large quantities, for example 100 pounds, of materials such as cement or the like, it is necessary to provide a sewing machine which -is not only capable of sewing through a considerable number of thicknesses of heavy krait paper, for example twenty or more, but is capable of accomplishing this very rapidly and of producing a tightly stitched seam.

It has been found that when it was attempted to employ sewing machines which had proven to be satisfactory for the sewing of cloth bags or the like, for the sewing of r'nulti-ply paper bags made of heavy kraft paper, such sewing machines proved unsatisfactory for several reasons. Aside from the fact that these machineswere insufflciently strong to perform the actual work, a

solution of the problem necessitated more radical re-design than could be effected by mere strengthening of the several parts thereof.

chines could not be adjusted to give sufficiently tightly stitched seams without creating a tendency to tear the paper being sewn or to break the stitching thread.

Moreover, it was also found that, whereas in previous sewing machines which operated satisfactorily on cloth bags, slight inaccuracies of movement of the feeding mechanism and the stitch-forming mechanism did not produce serious difliculties in sewing cloth, by reason of the more or less flexible or sleazy character of cloth as compared with paper, when such machines are of improved utility with respect'to sewing heavy and more or less rigid materials, such as the mouths of multi-ply bags formed from heavy paper or the like.

An object of my present invention is to provide further improvements in the design and op- It was found, for example, that such sewing maeration of sewing machines and sewing machine mechanism, whereby still more improved results may be secured, especially with respect to the sewing of heavy and rigid materials such as paper.

'A second object of my invention is to provide a sewing machine having improved stitchforming mechanism.

A further. object of my invention is to provide improved means for regulating the tension of the thread from which the stitching is formed, whereby paper or similar material may be provided with a firm and tight stitching without, however, placing too severe a stress upon the thread or causing the thread or stitching to damage or cut the material being sewn.

My invention has for further objects such additional improvements in operative advantages and results as may hereinafter be found to obtain. My invention is especially, although not necessarily, adapted to be employed in connection with a sewing machine having a feeding mechanism such, for example, as that described and claimed in the aforesaid application of Lincoln A. Cundall.and Robert N. Cundall, and having a needle adapted to reciprocate along an axis parallel to the axis of the main drive shaft of the sewing machine. In one aspect, my invention contemplates the provision of an improved looper mechanism adapted to cooperate with the aforesaid needle to form a stitch such, for example, as a so-called double-thread chain stitch, which mechanism is so designed as to impart an improved motion characteristic to the looper itself, thereby facilitating the, formation of the stitch and rendering the stitching more accurate and better adapted to the, stitching of more or less stiff or rigid material such as heavy paper.

' In another aspect, my invention comprises means for feeding thread to the aforesaid needle as required for the formation of the stitching, whereby the tension of the thread, as it is fed to the stitch-forming mechanism, is periodically varied in accordance with the movements of the stitch-forming mechanism, in such manner that paper or other stiff and; rigid material may be tightly stitched without injuring the material. More specifically, the thread-tensioning mechanism of my present invention contemplates the provision of a device for applying a normal tension, such as might be suitable for sewing cloth, to the needle.v thread during the entire sewing cycle, together with a second device or superimposing a heavier tension upon the needle thread during a portion of the cycle, the intermittent functioning of the second device being governed in accordance with the cycle of the needle, the looper and the feed mechanism.

In order that my invention may be clearly set forth and understood, I now describe, with reference to the drawings accompanying and forming a part of this specification, an improved form and. manner in which my invention may be embodied and utilized. In these drawings,

Fig. 1 is an elevational view of a sewing machine constructed in accordance with my present invention, the usual protective cover of the machine being removed in order to illustrate the moving parts of the machine more clearly;

Fig. 2 is an end-elevational view of a portion of the apparatus illustrated in Fig. 1;

Figs. 3 and 4 are vertical sectional views of the apparatus illustrated in Fig. 1, taken along the lines 3-4 and 4-4 of Fig. 1, respectively;

Fig. 5 is a horizontal-sectional view of a portion of the apparatus illustrated in Figs. 1, 3 and 4, taken along the line 5-5 of Fig. 1;

Figs. 6, 7 and 8 are plan, side-elevational and end-elevational views, respectively, illustrating more or less diagrammatically the relative positions of the needle, the looper and the material being sewed, at such time as the needle has been withdrawn from the material being sewed and is about to approach the same to form another stitch;

Figs. 9, 10 and 11; 12,13 and 14; 15, 16 and 1'1; 18, 19 and 20; and 21, 22 and 23, are similar views, respectively, illustrating the relative positions of the needle, the looper and the material being sewed, during subsequent portions of the stitching cycle, and illustrating the manner in which the stitch is formed;

Figs. 24 and 25 are enlarged sectional and sideelevational views, respectively, illustrating the appearance of the chain stitch formed by the movements of the needle and looper illustrated in Figs. 6 to 23 inclusive;

Fig. 26 is a horizontal sectional view of a portion of the apparatus illustrated in Fig. 1 taken on the line 26-26 of Fig. 1; and

Figs. 27 to 31 inclusive are diagrammatic motion studies of parts of the sewing machine from which a clear concept of the improved stitch forming mechanism may be obtained.

Similar reference numerals indicate similar parts in each of the several views of the drawings. It will be understood that while I have for convenience referred to the various figures as being in plan or elevation or in vertical or horizontal section, my improved sewing machine is adapted to be used in any position.

Referring now to the drawings, the sewing machine has a frame member or assembly I having the usual opening or throat 2 to permit the passage of material therethrough. A main drive shaft 3 is suitably journaled in bearings 4 and is provided with pulleys 5 and a hand wheel or fly wheel 6. The shaft 3 is preferably, but not necessarily, located with its principal axis normal to the plane of the material being sewn, which passes between a feed plate and an adjustable presser foot 8 mounted upon the usual presser foot rod 3.

The feeding of the material to be stitched through the machine is accomplished by means of a feed mechanism comprising in part a feed dog II which. in the present instance, is constructed and driven in the manner set forth and claimed in the aforesaid co-pending application of Lincoln A. Cundall and Robert N. Cundall. It will, however, be understood that while thls is the preferred feed, mechanism, other suitable feed mechanisms may be employed when so desired.

As set forth in the co-pending application of Lincoln A. Cundall and Robert N. Cundall, the feed dog II is attached to one end of an arm l3 5 which is mounted at its oppomte end upon a pin l3 extending parallel to the direction of move: ment of the material being sewn, in such manner as to be capable of motion both along and about the principal axis of the pin I3. The sliding mo- 10 tion of the member I2 along the pin I3 is derived from an eccentric device II mounted upon the shaft 3, which is connected by means of a pitman II to one end of a crank member I3 pivotally mounted upon a pin II iournaled in a lug I3 15 which is attached to the frame I. The end of the crank member It not connected to the pitman I 5 is provided with a slotted portion I3 through which passes a pin-member 2I biased by a spring 22. As the shaft 3 revolves, the eccentric I3 20 causes the crank member II to oscillate, thus reciprocally sliding the member I2 to and fro along the pin I3, and providing the feed dog I I with a component of motion in the direction of movement of the material to be sewn as well as 25 a component of motion in the opposite direction.

In order to cause the material being sewn to advance in a series of intermittent forward movements it is necessary for the feed dog II to be periodically retracted and advanced through 30 openings 23 in the feed plate I, the motion being such that the forward motion of the feed dog It takes place when the feed dog is advanced through the openings 23 to engage the material against the yielding support of the presser foot 3. At the 35 end of each forward stroke, the feed dog II must be retracted through the openings 23 out of en'- gagement with the material being sewn, in which i position it moves backward out of contact with the material being sewn in order to prepare for 40 another forward stroke.

The advancement and retraction of the feed dog I I through the feed plate I is accomplished by rocking the member I2 about the principal axis of the pin I3, and this is efl'ected by means of an 45 eccentric device 30 mounted on the shaft 3. The eccentric device 30 is connected by means of a pitman 3I to a block 32 adapted to reciprocate along a fixed straight path defined by a slot 33 formed by one or more members 34 attached to 59 the frame I. The block 32 is pivotally connected by means of a rigid "dumb-bell" link 35, having spherical heads at either end thereof, to the mem-' ber I2 at a point considerably removed from the pin I3. The spherical ends of the link a are 55 suitably journaled in recesses formed in the block 32 and the member I2, respectively.

It will thus be apparent that when the block 32 is reciprocated up and down as viewed in Figs. 1 and 4, the member I2 is reciprocally rocked about the pin I3. The combined effect of the reciprocal movements of the ends of the link 35 gives the feed dog II a closed-path motion, which path may be varied to a considerable extent by varying the relative positions and lengths of stroke of the members I2 and 32. In any event, however, the feed dog II is caused periodically to advance through the feed plate I to engage the material being sewn against the presser foot 8, then to advance the material being sewn by a distance equal to the distance between successive stitches, then to be withdrawn or retracted through the feed plate I out of engagement with the material being sewn and finally to return to its initial position ready to be the presser foot 6 in a series of short intermittent forward motions.

The stitch-forming mechanism comprises in part a needle. mounted upon one end of a needle bar slidably journaled in bearings 42 and 42, and having a principal axis normal to the plane of the material being sewn. The needle bar II is reciprocated along its axis by means of an eccentric device 64 comprising an eccentric cam, having a rounded face, mounted upon the main drive shaft 3 and which, through a pitman 45, a bell crank 46 pivotally mounted at 41, a link '5 and a block 49, drives the needle bar ll. The timing of the reciprocating motion of the needle bar II is such that the needle 66 enters the material being sewn just after each forward motion of the latter effected by the feed dog penetrates through the material for a suflicient distance to cooperate with other stitchforming mechanism to be described hereinbelow to form the beginning of a new stitch, and is then withdrawnfrom the material being sewn just prior to the time at which the feed dog again engages the material being sewn in order to advance into position for the next stitch. During the period of advancement of material being sewn, the needle 40 travels away from the material to the position illustrated in Fig. 1 and then returns, entering the material just after the forward stroke of the feeddog I I has been completed.

In order to form a double-thread chain stitc one thread is supplied to the material by means of the needle 40 while another thread is supplied to the opposite side of the material by means of a looper 5|, which cooperates with the needle 46 to cause an interweaving of the two threads on one side of the material being sewn, thus producing an interlocked stitch. In order to cause interlocking of the two threads, the

looper 5| is caused to travel in a closed path (which lies in an imaginary cylindrical surface generated about the pin 56 as an axis) drawn about an imaginary line comprising the principal axis of the needle 40 and needle bar 5|. In previous sewing machines having loopers for the purpose indicated, the motion of this closed path of the looper has ordinarily had the shape of a rather flat ellipse, but, according to my present invention, I provide improved mechanism whereby the path of the looper 5| may be made more or less oval in configuration in order to improve the accuracy and refinement of the manner in which the stitch is formed, and I now describe the mechanism whereby this result is obtained.

The looper 5| is held in a bifurcated clamp 52 having a suitable fastener 53. The opposite end of the clamp 52 is rigidly fixed by means of a set screw 54 or other fastening means to a member 55 which is mounted upon a pin 56 extending parallel to the stitching line, that is to say, parallel to the direction of movement of material being sewn. The member 55 is movable both about and along the principal axis of the pin 56.

It will be noted from inspection of Fig. 1, that in order to maintain the effective portion of the looper 5| at a uniform distance from the material being sewn, the looper 5| is curved on a radius extending to the center of the. pin 56. Since it is evident that the looper 5| thus pivots about the pin 56, it follows that the path of any fixed part of the looper 5| must be equidistant at any point from the axis of pin 56. It will, however, be understood that when reference is made herein to the substantially oval path of 5 the looper 5|, that such oval path lies .in an imaginary cylindrical surface, the radius of revolution of which depends upon the radial dis.- tance between the principal axis of the pin 56 and the looper 5|. a

' In the preferred instance shown, the motions of the member 55 both along and about the principal axis of the pin 56 are efiected by means of a single eccentric device 51 mounted upon and driven by the shaft 3. Attached to the ec- 15 centric device 51 is a pitman or connecting rod 58 which, at its lower end, passes through a sleeve member 59 pivotally mounted at one end upon a pin 60 secured to the frame I. As will be apparent from Fig. 4, therod 56 is free to move vertically with respect to the sleeve member 59 as the eccentric 51 rotates. However, as this occurs, the lateral movement of the rod 56, as viewed in Fig. 4, causes the sleeve member 59 to rock slightly about the pin 65;

The end of the sleeve member 59 opposite the pin 60 is pivotally attached by means of a pin 6| to a connecting link 62, the other end of which is eccentrically connected by means of a crank pin 63 to a member 65 adjustably mounted so on one end of a short shaft 65 journaled in a bearing 66 fastened to the frame I. The end of the shaft 65 opposite the member 64 is'bent at 61 and terminates in a yoke 68 operatively connected to a collar 69 which is freely mount- 95 ed on the pin 56 but is rigidly attached to the member 55.

Thus, as the shaft 3 rotates, the eccentric device 51, through the rod 58, causes the mem-v ber 59 to oscillate slightly about the pin 66, and 40 the effect of this oscillation of the member 59 operates through the member 62 and the crank pin 63 to oscillate the shaft 65 in the bearing 66, thus reciprocallymoving the member 55 to and fro along the pin 56 but without exerting any influence on the angularity of the member 55 with respect to the axis of the pin 56. For the purpose of providing an oscillatory movement of the member 55 about the principal axis of the pin 56, I provide a block 1| attached to the lower end of the rod 58. The block 1| is suitably recessed to receive one end of a socalled dumb-bell link 12, the opposite ends of which are spherical in shape. That end of the link 12 opposite the end pivotally secured to the block 1| is pivotally attached to the member 55, which is suitably recessed to receive the same.

It will be apparent from inspection of Fig. 1 that, as the eccentric device 51 causes the rod 56 and the block 1| to reciprocate in a substantially vertical line, this reciprocation of the block 1| will act through the link 12 to rock the member 55 about tha'e pin 56, thus raising and lowering the looper 5| as viewed in Fig. 1. It will be noted that in Fig. 1 the eccentric device 51 is shown at the top of its stroke, the block 1| being correspondingly at the top of its stroke and that in this position the link 12 is only slightly out of a Horizontal position as viewed in the drawings.

It will furthermore be apparent that as the block 1| moves downwardly it will have substantialy no eflect upon the member 55 until the link 12 is about as far below a horizontal position as it is shown above in Fig. 1, that is, on the opposite side of a horizontal plane passing through the 15 and of the link 12 which is attached to the member 05. In this latter position, the member 'H is not more than about half way down its path of travel. Consequently, during the first half of the downward stroke and the last half of the upward stroke of the member H there is relatively very little change in the angularity of the member ll about the pin it.

However, as the member H moves farther down toward the lower end of its stroke, the angularity of the link 12 with respect to the member 5' changes more rapidly and causes the member 55 to move more rapidly about the pin 58 in a clockwise direction as viewed in Fig. 1. Toward the end of the downward stroke of the member 1|, the turning movement of the member" slows down gradually, then gradually accelerates in the opposite direction as the member ll reci rocates and passes through the first half of its upward stroke.

It will thus be apparent that the looper BI is raised quite rapidly during such time as the block II is moving downward from a position midway of its path to a position near the bottom of its path and, conversely, the looper BI is rapidly lowered as the block H moves upward from a point near the bottom of its path to a point about midway of its path, while the movement of the looper II about the pin 56 is relatively very slow during the remainder of the path of travel of the block ll both at the top and bottom of its stroke.

It will further be apparent from the above, as well as from inspection of the drawings, that,

- due to the integrating effect of the member 55 on the translated motions of the member 1| and the member I8, the looper II passes through a closed path lying in an imaginary surface generated about the center of the pin 50, which closed path encloses an imaginary line forming an extension of the principal axis of the needle ll and-the needle bar 4|.

The timing and relative positioning of the various parts will be appreciated from an inspection of Figs. 2'7 to 31 inclusive. Fig. 27 represents the path of the needle tip along line A B,

entering the material at about 38 rotation of the main shaft and leaving it at about 322. Fig. 31 likewise is a study of the motion of the feed dog, the shaded portion indicating the operative part of the feed dogs travel when projected through the throat plate, the needle being at this time withdrawn. Fig. 28 represents the path of member ll, starting at D rotation of the main shaft) and reaching E (180 rotation) at its lowest point. Fig. 29 represents the path of the yoke 88, extending from F (90 rotation) and reaching G (270' rotation). Fig. 30 represents the path of the eye of the .looper in its relation to the needle which reciprocates normal to the plane of Fig. 30 at H. The lines D E and F G have been superimposed in correct relation to each other in dotted outline. It is to be noted that, due to the pivoting of arm 52 about pin II, the looper is at its highest position at 180' at the instant that member II is at its lowest point at E.

The dumb-bell link 12 plays an important part in determining the path of the looper and operates as follows. It will be apparent that for iforty degrees inclination more or less of the link 12 on each side of point D, the block II will have little or no effect on the looper. This is due to the fact that the dumb-bell link is of such a length and so positioned that it passes through a horizontal plane at 20, and for 20 on either side of this horizontal plane will neither push nor pull to any extent on member 5|. After passing 40', however, the link rapidly tends to assume a vertical position and pulls down the 5 back of member II to raise the looper until member H reaches E at 180. The return movement of the looper is identical but in reversed order, commencing at 180, traveling rapidly to about 320, and remaining stationary through 1 360.

During this time the yoke ll traverses its path F G reaching its extreme positions at 90 and 270. As both the dumb-bell link 12 and yoke 08 act upon the-looper the result will be to give it a mo- 15 tion along a closed path about the needle. This path is, from 90 to 270", the resultant of two forces traveling in straight lines at right angles with simple harmonic acceleration, and hence is a fiat ellipse. However, from 320 to 40 there is no vertical component so that portion of the path is a straight horizontal line.

The sequence is such that the looper, starting at 0, or for clarity, startingat 320, moves quickly horizontally to 40, moves quickly upward to 180 and then quickly downward to 320. This path may be defined as oval-shaped, or more accurately as an oval with a flattened end. The advantages arising from this will be more apparent hereafter.

The manner in which the looper cooperates with the needle to form a chain stitch may best be-understood with reference to Figs. 1 and 6 to 23, inclusive, in which the relative positions of the needle, the looper and the material being sewed are illustrated at a number of points in the stitch-forming cycle.

In Figs. 1, 6, '7 and 8, the needle 40 and looper 5! are illustrated at what may be called for purposes of explanation the beginning of the stitch- 40 ing cycle and which, for purposes of reference may be designated as 0 of rotation of the shaft 3. The material being sewn is designated by the reference numeral 15 and at this point is being r moved forward in the direction indicated by the 4 arrow by means of the feed dog II. The needle 40 is at this time well withdrawn from the material 15 and is about to move in the direction of the arrow, that is to say, toward the material being stitched, while the looper 5| is moving acrossthe stitching line in the direction opposite to the direction of movement of the material being sewn. It will be noted that the needle thread 16 passes from the needle through the last stitch in the material 15, around the looper 5| and back to the material being stitched,

while the looper thread 11 extends downward through the loop thereby formed in the needle thread 16 to the bottom of the looper and thence to the material being stitched.

In Figs. 9, l0 and 11, the needle 40, looper ii and material 15 are shown in positions which follow the positions illustrated in Figs. 6, 7 and 8', by about 80 of rotation of the shaft 3. The material 15 has now been moved forward by exactly the distance between successive stitches and is no longer engaged by the feed dog II but is stationary while the needle 40 has just pierced the material 15 for the next stitch. The looper 5| has now moved to a point lying to the rear of the needle 40 and is moving upward, and, as illustrated in Fig. 11, the movement of the looper 5| has formed a "thread triangle, two sides of which are formed by the looper thread 11 while the remaining side of the triangle is formed by the looped portion of the needle thread I. which extends from the previous stitch around the looper Ii and is held in position by points or about to enter the aforesaid triangle formed by the needle thread I8 and the looper thread 11.

Figs. 12, 13 and 14 illustrate the positions of the needle 40; the looper II and the material it at a position which corresponds to about 100 of rotation of the shaft 3 past the position illustrated in Figs. 1, 8, 'l and 8. The point of the needle 40 has now traversed the triangle formed by the looped needle thread 18 and the looper thread 11. The looper Ii is still rising and is about to rise to such position that the lower end of the looper 5i rises above the level of the needle 40 and it will therefore be apparent that the looper ii is about to strip itself of the looped portion of the needle thread It, the points onv the looper being no longer able to hold the thread.

. In Figs. 15, 16 and 17, the various parts are illustrated in a position corresponding to about 180 of rotationof the shaft 3 subsequent to the position illustrated in Figs. 1, 6, 7 and 8. At this time the needle 40 is near the point of maximum insertion through the material I! and the looper II has now reached a point above the needle 40, thus stripping off that portion of the-needle thread 10' which has heretofore been looped around the looper 5|. At this time, the looper I is moving forward, that is to say, in the general direction of movement of material being sewed, over and across the needle 40, that is to say, to the side opposite the side on which the looper Si is shown in Figs. 9 to 14, inclusive.

.Figs. 18, 19 and 20, represent a positionabout 50 of rotation of the shaft 8 past the position illustrated in Figs. 15, 16 and 1'7, or a total of about 230 of rotation subsequent to the initial position illustrated in Figs. 1, 6, 7 and 8, and

the needle 40 is now'being retracted rapidly through the material 15. It will be evident from inspection of Fig. 18 that that portion of the needle thread 16 which has just'been carried through the material bythe needle 40 is about to form a new loop on the forward side of the needle 40. The now descending looper 5|, having released the previous loop, is about to enter the newly formed loop in the needle thread 16. The needle is preferably provided with a slight indentation which the point of the looper may enter for this purpose.

In Figs. 21, 22 and 23, the needle 40, material I5, and looper 5i are illustrated in the positions in which they are found after about 300 of ro tation of the shaft 3 past the positions illustrated in Figs, 1, 6, '7 and 8. At this time, the point of the needle 40 is just about to be retracted from the material being sewed and the looper 5i has now descended through nearly all of its downward path. It will be further apparent that in thus descending, the looper 5i has passed through the looper portion of the needle thread 18 and will retain this looped portion of the mum area during-the time the looper passes from 320' through the position of Figs. 6, '1 and 8 to the position of Figs. 9, 10 and 11. There is thus formed a substantially large triangle which is retained for a long portion of a cycle and pre- 5 sents a large area for the needle to enter. This is of great advantage in that different timings of needle, looper or feed dog may be utilized to form variously altered stitches. It is also of great importance due to the relatively small 10 character of the worl; being performed as it allows slipping or vibrations to slightly alter the relative positions of parts without allowing the stitch forming parts to fail or drop a stitch.

In Figs. 21, 22 and 23, the feed dog is just 15 engaging the material II and is about to move forward in the direction indicated by the arrow a distance equal to the distance between successive stitches. A feature of my improved structure is that due to the curved shape of the looper and its operation in a generated surface, a more positive feeding device may be utilized. Thus while I have illustrated a feed dog having two short legs and one long leg, I may employ a feed dog having both its upper and lower legs 25 of greater length than the middle leg. This will give a greater gripping surface and hence'decrease the chances of the material slipping.

It will therefore be apparent to those skilled in the art, from inspection of the foregoing Figs. 6 to 23, inclusive, that the substantially flattened oval path of the looper 5|, comprising as it does, alternate substantially vertical and substantially horizontal motions in a closed path, and enclosing an imaginary line forming an extension of the principal axis of the needle 40, makes it possible, especially in combination with other features of my invention to be described hereinbelow, to produce a double thread chain stitch such as is more or less diagrammatically illustrated in Figs. 24 and 25 with the degree of precision and rigidity which is required in sewing relatively stiff materials such as heavy paper, and more especially in stitching the mouths of multi-ply kraft paper bags.

As has been stated hereinabove, in attempting to stitch heavy paper bags or ot er relatively stiff material, as distinguished fro soft material such as cloth, it has been found diflicult to obtain a tight stitching without putting sufilcient tension on the thread to injure the material being sewn. This is due to the fact that prior devices have provided for substantially uniform thread tension during the entire stitchforming period. When sewing light material such as cloth, the needle thread may be held under sufficient tension to give a considerable frictional drag on the thread as it is paid out in sewing. However, when sewing stiff, heavy materials, the needle thread is liable to break when the feed dog il pushes the material forward relative to the sewing machine against this heavy drag on the needle thread. This is particularly harmful and dangerous, especially when sewing such materials as paper which are fed through the machine in a series of intermittent jerking motions, and the material itself does not give readily but tends either to be torn by the thread or to break the thread depending upon the relative strength of the material and the thread.

According to my present invention, means are provided whereby any paying out of the needle thread may be resisted by a light tension during such portion of the stitch-forming period in A the device I02.

which the feed mechanism is advancing the material relative to the sewing machine, andby a considerably greater tension during such time -eyes III to the needle 00.

The disc III is mounted upon one end of a, leaf III, and is urged toward the disc IIO by means of a spring I" mounted upon an adjustable supporting member I I0 preferably located about mid way of the leaf 5. A block II! is provided for limiting the'travel of the leaf I IS.

The disc III is mounted upon a short sliding pin I2I, suitably journaled in the frame member I and terminating in a rounded end I22 which bears against the face of a cam member I23 attached to one end of the shaft}.

Thus, as the shaft 3 rotates, the cam m will act upon the end I22 of the pin I2I to urge the disc III against the flexibly biased disc III, thus placing the thread 16 under the tension of the spring I" during one portion of the period of the rotation of the shift I, that is to say, during a portion of the stitch-forming cycle, and during another portion of the cycle will relieve the disc H0 and the thread 16 from the pressure of the spring III exerted through the biased disc III. III is suitably adjusted in accordance with the character of the material being sewn and the tightness of the stitch desired.

The cam I23 is so designed that it causes the discs III and III to be pressed together at such time as the needle 00 is moving forward to penetrate the material being sewn, while relieving the;

additional tension upon the needle thread I8 during such time as the needle is being retracted out of the material being sewn and the feed dog II is advancing the material relative to the sewing machine. During this period in which the feed dog is moving the material being sewn, the material itself tends to drag the thread away from the needle and it would obviously cause too great a force to be applied to the thread were this force exerted by the feed mechanism to be allowed to oppose the relatively heavy tensional force which is necessarily applied to the needle thread during such time as the needle is penetrating the material being sewn. s

In the preferred instance (diagrammatically illustrated in Fig. 27) the cam I23 is so designed that the needle thread I6 is maintained under the tension resulting from the compressive force of the spring II'I acting through the discs H0 and III over somewhat less than half of the total stitch forming period or, more specifically, over approximately 158 of rotation of the shaft 3. During the remaining 202 of rotation of the shaft 3 the paying out of the needle thread is resisted merely by the tensional force exerted by In this instance the needle 40 enters the material being sewn at approximately 38' of rotation of the shaft 3 past the zero or starting position illustrated in Figs. 1, 6, 7 and 8, and the discs H0 and III grip the thread at The pressure exerted by the springapproximately 16 of rotation of the shaft; prior to the point at whiclr the needle enters the, material or, in other words, at 22 of rotationv of the shaft 2 past the zero position illustratedin Figs. 1, 6, 7 and 8. At this pointthe feed dog II has reached its maximum forward feed-. ing position and is about to travel away from the presser foot 8.

As the cycle proceeds, the cam I 23 causes the discs H0 and III to be separated at 180 of rota- 10 5 tion of the shaft 3 past the zero position, at which. time the needle has reached its maximum forward position (to the right as viewed' in Fig. l) and the feed dog II is at its maximum rearwardv position and is about to move toward the presser' foot 0 to grip the material and advance it forward. The feed dog II does not, however, engage the material being sewn and give it anotherforward movement untilthe needle 40 is withdrawn from the material. The portion of the needle stroke during which the thread is under tension from the discs is illustrated as part C of Fig. 27. The discs are held apart as the needle travels from 180 through 322 (when the needle leaves the material), through 0 (when the nee- 2 die starts the next cycle), until 22 of the next cycle is reached.

It will be understood by those skilled in the art that the term tension as employed hereinaboveis not intended to mean that the device I02 or the discs H0 and III exert a force tending'to draw the needle thread back through the needle 40 at any time, but merely that the device I02 and the discs H0 and I II, when they are actuated to do so, exert a frictional drag upon the needle thread It which resists paying out of the thread to a greater or less extent depending upon whether only the device I02 acts upon the thread I6 or frictional force exerted by the device I02 issupplemented by the drag put upon the thread I6 by the spring III acting through the H0 and III.

As illustrated in the drawings, and more particularly Figs. 1, 2 and 26 thereof, my novelmeans for varying the tensional drag on the needle thread in accordance with the requirements encountered in sewing heavy paper bags or the like, has been shown in combination with a thread take-up mechanism set forth and described in the co-pending application of Paul Kuhlig, Ser. No. 646,436, filed December 9, 1932. While my invention is not limited to use in combination with the device set forth and claimed in the aforesaid application of Paul Kuhlig, nevertheless, its advantages and utilities are considerably enhanced, and the operation of the sewing machine'as a whole is rendered more advantageous when my device is thus combined with the aforesaid thread take-up mechanism, and, therefore, I now briefly describe the nature and manner of operation of the aforesaid thread take-up mechanism, as well as the manner in which my novel thread-tension relief mechanism cooperates therewith.

Referring now to Figs. 1 and 26, the aforesaid thread take-up mechanism comprises a cam I which is mounted on a tubular extension I5I suitably secured to the frame I and projected outwardly therefrom. One side of this tubular extension I5I is provided with a slot I52 in which the eye II3 on the reciprocating needle bar 4| travels.

The cam I50 is designed to permit a. limited amount of slack in the thread 16 at the start of the forward reciprocation of the needle bar I and the needle 40. some slack being necessary for 75 the formation of a loop by the needle. It is also so designed that after the needle bar lI reciprocates, the cam I50 takes up the slack in the needle thread I and permits it to be paid out as required, thereby avoiding breaking of the thread or tearing of the material being sewn. It is also so designed that upon retraction of the needle bar I, the needle thread I0 is taken up sufficiently to withdraw a portion thereof back through the eye of the needle 40 and to decrease the size of the loop formed by the needle and insure being properly caught by the descendlngloo'p'er This'cam I50 also cooperates with the" moving eye I Ilin such manner that as the needle bar 4| continues to be retracted the stitch just formed is drawn tight.

To accomplish these purposes, the cam plate I50 may be of various formations. but as shown in Fig. 26 has a substantially circular salient cam portion I51 on the side nearest the needle 40 and a receding cam portion I54 on the side remote fromthe needle 40.

In the position illustrated in Fig. 1, in which the needle 40 is shown in its fully retracted position,

I that portion of the needle thread I5 between the tubular guide H2 and the eye III is wholly free from the cam I50 and the needle thread I6 does not engage the cam I50 until the needle bar 4| and the eye II3 have moved forward a short distance to the position of Fig. 2. It will therefore be apparent that this free movement of the eye I I3 between the point of engagement of the needle thread I0 with the cam I50 and the fully retracted position of the eye II3, upon retraction of the needle 40, provides for paying out the necessary amount of thread for the next ensuing stitch and, on the immediately succeeding forward movement of the needle 40 and the eye 3, for the limited slack in the needle thread I5 which is necessary for the subsequent formation of the loop forming the upper side of the thread triangle which increases in length as the looper travels from the position of Fig. 8 to the position of Fig. 11.

As the needle 40 and the eye III move forward, that is to say to the right as viewed in Fig. l, the needle enters the material and enters the triangle of thread shown in Figs. 9 to 14. During this movement, the length of the needle thread I6 between the eye I I3 and the outlet of the tubular guide H2 is caught by the portion I54 of the cam I50 and is deflected outwardly of the cam I50 as in Fig. 2. One of the reasons for the additional tensioning device is now apparent, this reason being that the side of the thread triangle formed by the loop in the needle thread I6 (Fig. 11) must be maintained in a tight condition during the relatively long period of time during which the area of the thread triangle is maintained at its greatest and the needle is entering the triangle. As seen in Fig. 11, this needle thread loop is maintained in position on the face of the then rising looper 5I by the points or slight elevations on the face of the looper. These slight elevations would not be sufficient to hold the loop if the thread were not under greater tension than normal, and as seen in Fig. 27, this portion of the cycle is within the portion C when the full tension is applied. It is thus made certain that the thread triangle will be maintained during the relatively long period of time from its formation to its being stripped from the looper, and conversely that the needle thread loop will be positively stripped from the looper (Figs. 14 and 1'7), and the machine is thereby prevented from dropping stitches, or from mixing stitches, or from breaking the mechanism or threads.

As the needle 40 moves forward still farther, the length of thread between the end of the tubular guide H2 and the eye II! passes around 5 the salient portion I53 of the cam I50, and, as the needle reaches its fully projected position, the length of thread between the outward end of the tubular guide H2 and the eye Ill slips around the rounded salient .portion I53 of the cam I50 and rides down to the base of the cam adjacent the tubular support I5I, the tension devices III and I I I, being operative up to this point (Fig. 27).

As the needle 40 then starts its return stroke, the cam I50 cooperates with the retracting eye 15 III to draw upon the loop being formed by the needle in so retracting, and thereby limiting the size of the loop (Fig. 18). This prevents the formation of an excessively large loop by the needle in retracting, which large-size loop, if per- 20 mitted-to be formed in high speed sewing, would be liable to drop down and not be caught by the looper 5I, thereby causing the sewing machine to drop a stitch.

As the needle 00 continues to be retracted, the slack in the needle thread It continues to be drawn up by the cam I50, thus drawing the just formed stitch tightly against the material being sewn. However, at this time, the cam I23 acts to separate the discs H0 and III, thereby preventing the combined force exerted by the feed mechanism and the cam I50 from imposing so great a force upon the needle thread I6 as to break the same or to injure the material being sewn.

During the final retracting movement of the needle 40, as set forth hereinabove, the needle thread I5 is drawn free from the cam plate I to the starting position illustrated in Fig. 1 thereby paying out additional thread from the source of supply for the formation of the next succeeding stitch.

From the foregoing, it will be apparent that my invention provides improved means for stitching relatively heavy and rigid materials such as multiply paper at high speed. My invention contributes to the accuracy of the stitch formation and to the ease and facility with which a relatively tight stitch may be accomplished without injury to the thread or the material being sewn.

While I have hereinabove described my in- 50 vention with respect to a. preferred embodiment thereof it will readily be understood by those skilled in the art that my invention is not limited to the details of this embodiment but may variously be utilized and embodied within the scope of the claims hereinafter made.

I claim:

1. In a sewing machine for forming a doublethread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a. looper mounted for motion both along and about an axis extending parallel to the direction of movement of the material being sewn, said looper being curved radially with respect to said axis, and actuating means for said looper adapted to cause it to move alternately along and about said axis in a closed path in the shape of an oval with a flattened end, the movement across said flattened end being timed to occur as the needle and looper co-operate to form a stitch whereby substantial movement of said looper is avoided as the stitch is being formed.

2. In a sewing machine, means for feeding material therethrough in a series of intermittent movements, a thread-carrying needle adapted to be reciprocated to pierce said material and be withdrawn therefrom between successive movements of said material, with respect to the sewing machine, thereby forming a thread loop, a looper carrying a second thread and mounted on a pin having a principal axis extending parallel to the plane of the material being sewn, and means adapted to reciprocate said looper in alternate harmonic movements along and about said axis to cooperate with said needle to form a line of stitching, said means comprising a drive shaft, an eccentric device mounted on said shaft, a connecting rod driven by said eccentric device, and means for translating the longitudinal and lateral reciprocation of said rod produced by said eccentric device to said looper to produce reciprocal motions in one direction and alternate reciprocal motions in a direction normal to said first-mentioned direction comprising a dumbbell link connecting said looper and said connecting rod and mounted to pass through a horizontal plane during the time that the needle approaches the looper whereby substantial movement of said looper is avoided during the time that the stitch is being formed, the resulting motion of said looper defining an oval path with a flattened end.

3. In a sewing machine, means for feeding material to be sewn through said machine in a series of intermittent movements, a thread-carrying needle adapted to pierce said material and be withdrawn therefrom between successive movements of said material with respect to the sewing machine, and means for controlling the tension of the needle thread as it is paid out by the needle motion, comprising a device adapted to impose a constant frictional drag upon-the needle thread, a second device adapted to impose an additional frictional drag upon the needle thread and means actuated in timed relation to the movement of said feeding means and said needle for releasing said thread from the additional frictional drag of said second device during such time as the material being sewn is advancing relative to the sewing machine.

4. In a, sewing machine, means for feeding material therethrough in a series of intermittent movements, 9. thread-carrying needle adapted to be reciprocated to pierce said material and be withdrawn therefrom between successive move-' ments of said material with respect to the sewing machine, a looper carrying a second thread, a holder therefor mounted on a pin having a principal axis extending parallel to the direction of movement of the material being sewn, means adapted to reciprocate said looper in a closed path to cooperate with said needle to form a line of stitching, said means comprising means for reciprocating said looper holder to and fro along said pin, a member adapted to be reciprocated along a line at right angles to the direction of movement of said needle and the principal axis of said pin, and a link pivotally connected at its opposite ends to said looper holder and said reciprocating member.

5. In a sewing machine, means for feeding material therethrough in a series of intermittent movements, a thread-carrying needle adapted to be reciprocated to pierce said material and be withdrawn therefrom between successive movements of said material with respect to the sewing machine, a looper carrying a second thread,

aholder therefor mounted on a pin having a principal axis extending parallel to the direction of movement of the material being sewn, means adapted to reciprocate said looper in a closed path to cooperate with said needle to form a line of stitching, said means comprising means for 5" reciprocating said looper holder to and fro along said pin, a member adapted to be reciprocated along a line at right angles to the direction of movement of said needle and the principal axis of said pin, and a link pivotally connected at its opposite ends to said looper holder and said reciprocating member,.said looper holder reciprocating means and said member being actuated in timed relation to each other. I)

6. In a sewing machine, means for feeding 1' material therethrough in a series of intermittent movements, a thread-carrying needle adapted to be reciprocated to-pierce said material and be withdrawn therefrom between successive movements of said material with respect to the sewing machine, a looper carrying a second thread, a'holder therefor mounted on a pin havinga principal axis extending parallel to the direction of movement of the material being sewn, means adapted to reciprocate said looper in a closed path to cooperate with said needle to form a line of stitching, said means comprising means for reciprocating said looper holder to and fro along said pin, a member adapted to be reciprocated along a line at right angles to the direction of 30 movement of said needle and the principal axis of said pin, and a link pivotally connected at its opposite ends to said looper holder and said reciprocating member, said looper holder reciprocating means and said member being actuated 35 in timed relation to each other to produce a series of alternated movements of said looper holder along said pin and about said pin, respectively.

7. In a sewing machine, means for feeding material therethrough in a series of intermittent 40=- movements, a thread-carrying needle adapted to be reciprocated to pierce said material and be withdrawn therefrom between successive movements of said material with respect to the sewing machine, a looper carrying a second thread, a holder therefor mounted on a pin having a principal axis extending parallel to the direction of movement of the material being-sewn, means adapted to reciprocate said looper in a closed path to cooperate with said needle to form a line of sitching, said means comprising a main drive shaft rotating in timed relation to said needle, an eccentric mounted thereon, a member connected thereto adapted to reciprocate along a line a right angles to the needle, a rigid link pivotally connected at its opposite ends to said looper holder and said member, respectively, and means operating in timed relation to the rotation of said main drive shaft for reciprocating said looper holder to and fro along said pin. on

8. In a sewing machine, means for' feeding material therethrough in a series of intermittent movements, a thread-carrying needle,adapted to be reciprocated to pierce said material and be withdrawn therefrom between successive movements of said material with respect to the sewing machine, a looper carrying a second thread,

a holder therefor mounted on a pin having a principal axis extending parallel to the direction of movement of the material being sewn, means adapted to reciprocate said looper in a closed path to cooperate with said needle to form a line of stitching, said means comprising a main drive shaft rotating in timed relation to said needle,

an eccentric mounted thereon, a member con.- 5-

V 2,048,149 nected thereto adapted to reciprocate along a line a right angles to the needle, a rigid link pivotally connected at its opposite ends to said looper holder and said member, respectively, and a second eccentric device actuated .b d main drive shaft adapted to reciprocate said looper holder to and fro along said pin.

9. In a sewing machine, a needle bar having a thread-carrying needle adapted to be alternately advanced into and retracted from the material being sewn, a first tension device for.

imposing a constant frictional drag upon the needle thread, a second tension device for intermittently imposing additional frictional drag upon the needle thread, means comprising a fixed thread-engaging cam mounted adjacent said-needle bar for taking up slack in the needle thread between said devices and said needle as the latter is withdrawn from its fully advanced position to its fully retracted position and vice versa, and meansfor releasing the additional frictional drag exerted upon said thread by said second tension device during the time that said needle is being retracted from the material.be

. ing sewn.

10. In a sewing machine, a needle carrying a needle thre'ad, means to thrust said needle through the material being sewn during each cycle of the machine at stitching intervals, a

loo'per carrying a looper thread and cooperating with said needle to form a stitch at each cycle of the machine, said needle and looper cooperating at the end of one cycle to provide a thread triangle defined on two sides by said looper thread and on the other side by a loop of said ..needle thread passed around said looper, which insure maintenance of the area of said thread triangle at a maximum during a'substantial portion of a cycle and insure the stripping of said 20 loop from said looper after the needle has fully penetrated said triangle, and said second tension device being rendered inoperative prior to the formation of the succeeding thread triangle in order that a suflicient length of needle thread 25 may be pulled through the needle to form the loop comprising the thread side of the succeeding thread triangle.

' HOWLAND F. BRIGGS. 

